How to use btrfs to speed up Android development with a crontab job.

del-old-snapshots.sh

#!/bin/bash
# Delete old snapshots except the newest one

# Replace product and variant as needed

del_product () {
    read -a FILES <<< `ls -dt $1_BUILD_$2_*`
    unset FILES[0] # Do not delete newest
    for dir in ${FILES[*]}
    do
        echo "Deleting $dir"
	sudo btrfs subvolume delete $dir
    done
}

del_product product variant

update-golden.sh

#!/bin/bash -x

dt=`date +"%Y%m%d"`

echo "Number of parameters: $#"
if [ "$#" -eq 4 ]; then
	LOG_FILE=${dt}_$4
else
	LOG_FILE=/tmp/log_${dt}.txt
fi

if [ "$#" -lt 3 ]; then
	echo "Needs disk and product name and build variant."
	echo "Parameters: $1 $2 $3 $4"
	echo "Usage: $0 <btrfs dir> <product> <variant> [<log file>]"
	exit 1
fi

exec 3>&1 4>&2
trap 'exec 2>&4 1>&3' 0 1 2 3
exec 1>$LOG_FILE 2>&1

BTRFS_DIR=$1
PRODUCT=$2
VARIANT=$3

GOLDEN_DIR=${BTRFS_DIR}/${PRODUCT}_BASE_VOL
BUILD_DIR=${BTRFS_DIR}/${PRODUCT}_BUILD_${VARIANT}
LUNCH=${PRODUCT}-${VARIANT}

echo $GOLDEN_DIR
echo $BUILD_DIR
echo $LUNCH

pushd $GOLDEN_DIR

if ! /usr/local/bin/repo sync -j 4 --force-sync; then
	echo "Repo sync failed. Exiting."
	exit 2
fi 

# Make backup of old build dir just in case.
if [ -d $BUILD_DIR ]; then
    mv $BUILD_DIR ${BUILD_DIR}_$dt
fi

# Create snapshot for building
/bin/btrfs subvolume snapshot $GOLDEN_DIR $BUILD_DIR

# Build SW
cd $BUILD_DIR
source build/envsetup.sh
lunch $LUNCH
cook all

popd